1. Field of the Invention
The present invention is directed to a thrust plate assembly for a motor vehicle friction clutch with automatic wear compensation including a housing that is fixedly connectable to a flywheel for joint rotation with the flywheel about an axis of rotation, a pressure plate arranged in the housing such that the pressure plate is fixed with respect to rotation relative to the housing and axially displaceable relative to the housing, an energy accumulator having one side supported at the housing and another side supported at the pressure plate, and a wear adjustment device arranged in the support path of the energy accumulator between the energy accumulator and a component of the housing and pressure plate and including at least one adjustment element which is displaceable to compensate for wear, the wear adjustment device being operatively arranged for compensating for wear in proportion to the occurring wear.
2. Description of the Related Art
A prior art thrust plate assembly is disclosed in German reference DE-A-29 20 932 having a wear adjustment device with an adjustment ring with a plurality of surface regions arranged successively in circumferential direction. These plural surface regions are inclined relative to the circumferential direction and contact corresponding counter-surfaces of a pressure plate which are inclined relative to the circumferential direction. During a rotation of this adjustment ring in circumferential direction, i.e., in a wear adjustment movement direction, the surfaces and counter-surfaces slide against one another so that the adjustment ring is displaced axially in relation to the pressure plate and compensates, e.g., for wear occurring in the region of friction facings. The adjustment ring is pretensioned by an adjusting spring for movement in the circumferential movement direction. In this known thrust plate assembly, an area of a diaphragm spring acting on the adjustment ring is swiveled during a disengaging or releasing movement and the pressure plate follows this movement of the diaphragm spring essentially completely. However, if wear which is detectable by a play sensor of the thrust plate assembly has occurred previous to the disengaging movement, the release path of the pressure plate is limited so that at the end of the movement travel or lift of the diaphragm spring, the pressure plate no longer follows this lift and the wear adjustment device, i.e., the adjustment ring, is consequently released for carrying out the compensating movement mentioned above. The extent to which the pressure plate no longer follows the lifting off movement of the diaphragm spring corresponds precisely to the wear previously detected by the play sensor. The precise amount of this release path that is no longer traveled is compensated by the wear adjustment device. Therefore, the adjustment ring initially directly contacts the diaphragm spring again during an engagement process to be carried out subsequently and finally the diaphragm spring acts upon the subassembly formed of the pressure plate and adjustment ring to the precise extent and manner as with a clutch disk which does not exhibit any wear. Even when wear occurs, the installation position of the diaphragm spring does not change over the life of a thrust plate assembly of this type so that the releasing force required remains essentially the same and the clutch characteristic remains essentially unaltered.
An object of the present invention to provide a thrust plate assembly which has an improved capacity for adapting to operating conditions which change over the operating life of a clutch.
The object is met according to an embodiment of the present invention by a thrust plate assembly for a friction clutch in a motor vehicle with automatic wear compensation, comprising a housing fixedly connectable to a flywheel for joint rotation with the flywheel about an axis of rotation, a pressure plate arranged in the housing such that the pressure plate is fixed with respect to rotation relative to the housing and axially displaceable relative to the housing, an energy accumulator such as a diaphragm spring having one side supported at the housing and another side supported at the pressure plate, and a wear adjustment device arranged in the support path of the energy accumulator between the energy accumulator and a component of the housing and pressure plate. The wear adjustment device has at least one adjustment element which is displaceable to compensate for wear and is operatively arranged for effecting wear compensation in proportion to the occurring wear.
In the thrust plate assembly according to the present invention, the ratio of movement of the wear adjustment device to the amount of wear differs from 1:1.
As was already noted, the axial expansion of the subassembly formed of the pressure plate and adjustment ring when carrying out wear compensation in the prior art is exactly the same as the extent to which friction linings become thinner. However, it has been determined that other characteristics of the thrust plate assembly which change over its useful life are not accounted for by this arrangement. It has been recognized, for example, that the operating characteristic, i.e., force characteristic, of a spring element such as an energy accumulator changes over the operating life. This property of the spring element is taken into account by the present invention in that a compensation process is not implemented in a ratio of 1:1 to the actually occurring wear. Rather, it is ensured by diverging from this ratio of 1:1 in a defined manner that the installation position of the energy accumulator changes in spite of the occurrence of wear and the execution of a compensating movement compelled by the occurrence of wear.
According to the present invention, when a spring force decreases in a determined installation position due to fatigue, wear compensation may be effected to a determined degree while simultaneously bringing the energy accumulator into a position which allows the spring to generate a higher force than in the original installation position, i.e., in the new state. Therefore, the defined selection of the ratio, which now no longer takes into account the exact wear actually occurring, accounts for many different variables which are known to change over the operating life of a clutch. In this way, the operating characteristic of a thrust plate assembly of this type and a clutch outfitted with this thrust plate assembly may be maintained in an improved manner.
The thrust plate assembly according to the present invention may, for example, comprise at least one adjustment element that is movable in a wear adjustment movement direction corresponding to occurring wear and that the movement in the wear adjustment movement direction causes a displacement of at least one adjustment element in a compensating movement direction different than the wear adjustment movement direction, and that the extent of movement in the compensating movement direction for wear and the wear itself is in a ratio other than 1:1.
A desired ratio between the wear which occurs and is detected and the compensation that is actually implemented is achieved in that the at least one adjustment element moves in the wear adjustment movement direction with a surface inclined in the wear adjustment movement direction along a counter-surface. Alternatively, the desired ratio may be achieved in that the at least one adjustment element moves along a counter-surface inclined in the wear adjustment movement direction. In both cases, the angle of inclination of the surface or counter-surface is selected in such a way that the extent of movement in the compensating movement direction is in a ratio to wear other than 1:1.
To detect wear in operation, the thrust plate assembly according to the invention may have at least one play sensor arrangement with a detection element having a detection portion arranged for interacting with a component or subassembly for detecting wear. The component or subassembly with which the detection portion is interactable is displaceable with respect to another component when wear occurs. Therefore, when wear occurs, the detection element is positioned corresponding to the wear detected by the interaction with the component or subassembly.
To achieve the desired stopping of the movement of each detection element, an embodiment of the present invention includes a stopping element displaceable in a stopping movement direction by a movement extent or distance corresponding to the wear to stop the detection element when wear occurs. The stopping element has a blocking member for cooperating with the at least one adjustment element to limit the movement of the adjustment element in the wear adjustment movement direction to an extent corresponding to the wear.
The wear adjustment movement direction of the at least one adjustment element is in the same direction as the movement of the stopping element in the stopping movement direction so that the cooperation between the stopping element and the at least one adjustment element in the simplest possible manner.
For example, the stopping movement direction and the wear adjustment movement direction may correspond essentially to a circumferential movement direction. The blocking member then preferably forms a stop acting substantially in the wear adjustment movement direction. In this arrangement, the stop acts directly in the direction in which the at least one adjustment element moves under pretensioning to effect a compensating movement. In contrast to the prior art in which the generated compensating movement, i.e., the axial movement, is directly limited by a stop which acts axially in a corresponding manner, the present invention limits a movement which may, for example, be in the circumferential direction which does not necessarily require an axial stop. Therefore, the movement in the compensating movement direction, i.e., the actual axial expansion of the wear adjustment device, may be configured to be different than the wear that has occurred in any desired manner. The movement in the compensating movement direction is decoupled from a determined extent of axial movement and the extent of axial movement is predetermined by this movement in the wear adjustment movement direction.
The stopping element may, for example, be wedge-shaped with an angle of the wedge-shaped stopping element differing from an angle of inclination of the surface or counter-surface. Therefore, a movement distance of the stopping element in its stopping movement direction is equal to the movement distance of the at least one adjustment element in the wear adjustment movement direction. However, the axial expansion of the wear adjustment device or of the subassembly formed of the pressure plate and the at least one adjustment element which occurs is different from the actual or detected wear because of the different angle of inclination between the wedge-shaped stopping element and the surface or counter-surface. Accordingly, the ratio differing from 1:1 is achieved.
In a further embodiment, one of the wedge angle of the stopping movement direction and the angle of the surface/ counter-surface may be arranged so that it is not constant in the wear adjustment direction. This allows characteristics of the thrust plate assembly which do not change linearly over the operating life of a thrust plate assembly of this kind to be taken into account.
In particular, if the setting of a spring used as energy accumulator is to be taken into account with the present invention, the ratio is less than 1:1 and preferably in the range including 0.6 to 0.95.
As discussed above, the ratio may change as compensation of wear increases, i.e., over the operating life of the thrust plate assembly, to take into account influencing variables which do not change linearly. For this purpose, the ratio preferably increases as the compensation of wear increases. The increase of the ratio as the compensation of wear increases allows the influence of xe2x80x9cspring settingxe2x80x9d, as it is called, to be accounted for in which springs, e.g., diaphragm springs, which are used as energy accumulators change their characteristic relatively dramatically in the initial phase of their operating life and remain virtually unchanged or change only slightly after this initial relatively sharp change in characteristic.
According to another embodiment of the present invention, the object is met by a thrust plate assembly for a motor vehicle friction clutch with automatic wear compensation, comprising a housing fixedly connectable to a flywheel for joint rotation jointly with the flywheel about an axis of rotation, a pressure plate which is arranged in the housing so that the pressure plate is fixed with respect to rotation relative to the housing and is axially displaceable relative to the housing, an energy accumulator such as a diaphragm spring having one side supported at the housing and another side supported at the pressure plate, and a wear adjustment device arranged in the support path of the energy accumulator between the energy accumulator and a component of the housing and pressure plate. The wear adjustment device has at least one adjustment element displaceable to compensate for wear and is pretensioned for movement in a wear adjustment movement direction. When the wear adjustment device moves in the wear adjustment movement direction, a surface of the at least one adjustment element inclined in the wear adjustment movement direction moves along a counter-surface. Furthermore, the at least one adjustment element may be blocked by at least one blocking member to prevent movement in the wear adjustment movement direction. The thrust plate assembly further comprises at least one play sensor arrangement for detecting wear, wherein the at least one play sensor arrangement comprises a detection element which interacts with or can be made to interact with a component or subassembly for detecting wear. The component or subassembly is displaceable with respect to another component of the thrust assembly when wear occurs so that the detection element is brought into a position corresponding to the wear by the interaction with the component or subassembly.
This thrust plate assembly includes a stopping element for stopping the detection element of the at least one play sensor arrangement in its position corresponding to the wear. Furthermore, the at least one blocking member is provided at the stopping element.
According to this embodiment, a blocking of the movement of the at least one detection element is not required to act in axial direction as was the case in the prior art. Therefore, a desired conversion of the amount of detected wear into the compensating movement associated with the operating life may be effected.
For this purpose, the at least one blocking member may be arranged to interact with the at least one adjustment element so as to block essentially in the wear adjustment movement direction.
The counter-surface may be formed at the one component on which the wear adjustment device is arranged. Also, the at least one detection element may be arranged with a detection portion for interacting with the component or subassembly. For example, the component or subassembly that interacts with the detection element may comprise the housing or the energy accumulator or any component which moves relative to the pressure plate when wear occurs.
At least a portion of the detection element may be located between the at least one adjustment element and the one component on which the adjustment element is arranged. The at least one adjustment element may, for example, comprise an adjustment ring which is arranged substantially concentric to the axis of rotation. Furthermore, the one component is the pressure plate and the detection portion of the at least one detection element projects through an intermediate space formed between the adjustment ring and the pressure plate. Further, the stopping element is displaceable in a stopping movement direction when wear occurs by a movement amount corresponding to the wear to stop the detection element in its position corresponding to wear. In this respect, it is preferable for the wear adjustment movement direction of the at least one adjustment element to be the same direction as the stopping movement direction of the stopping element. The wear adjustment movement direction and the stopping movement direction is preferably a circumferential direction.
The present invention is further directed to a friction clutch with a thrust plate assembly according to the present invention.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.